Selective call signaling systems (e.g., paging systems) provide one-way radio frequency (RF) communication of selective call messages, called pages, from a message originator to a paging receiver. The message originator contacts the paging system via the public switched telephone network system or other input interface means and provides the message information to a paging terminal. The message information is encoded into a conventional signaling protocol, modulated onto a carrier signal, and transmitted as an RF signal to the paging receiver. The paging receiver receives the signal, demodulates and decodes the signal to recover the messages and presents the message to a user of the receiver.
Air time is a precious commodity in selective call signaling systems. A selective call system service provider wishes to provide service for a large number of subscribers (receiver users) in order to obtain high revenue. With short voice and numeric messages, the length of the message has not had an impact on message throughput. However, alphanumeric messages can pose a difficulty. Page entry devices for alphanumeric messages include personal computers which can generate extremely long messages. In addition, originators may wish to send longer voice messages, graphic images and facsimile messages.
To increase message throughput of longer messages, the data rate of the paging system can be increased. Yet the data rate has limitations imposed by the performance of wide area paging systems. For example, the inter-symbol interference generated by multipath distortion becomes a significant limiting factor in simulcast paging systems when the data rate is increased beyond six kilobits per second.
In addition, the data rate has limitations imposed by governmental regulatory agencies such as the United States Federal Communications Commission (FCC). For example, inter-channel interference can be generated by high data rate signals, and the FCC can specify maximum power of signal emissions (translating to specifying maximum data rates of signals) if the inter-channel interference rises above a certain level.
Thus, what is needed is a high data rate transmission scheme for handling lengthy alphanumeric, voice, graphic, and facsimile selective call messages.